Not Applicable.
Not Applicable.
Not Applicable
1. Field of the Invention
This invention relates generally to driver circuits, and, more particularly, to driver circuits having tristatable outputs that are suitable for use in automatic test equipment.
2. Description of Related Art Including Information Disclosed Under 37 C.F.R. 1.97 AND 1.98
Automatic test equipment (ATE) plays a significant role in the manufacture of semiconductor devices and circuit board assemblies. Manufacturers generally use automatic test equipment, or xe2x80x9ctesters,xe2x80x9d to verify the operation of electronic units during the manufacturing process. Early detection of faults eliminates costs that would otherwise be incurred by processing defective units, and thus reduces the overall costs of manufacturing. Manufacturers also use ATE to grade various specifications. Units can be tested and binned according to different levels of performance in significant areas, for example, speed. Units can then be labeled and sold according to their actual levels of performance.
The instant invention relates to driver circuits for ATE. Testers employ driver circuits for many uses. Perhaps the most prevalent use is for stimulating devices under test (DUTs) during the execution of test processes. Stimuli from driver circuits can be provided in the form of analog or digital signals, and can cover a potentially wide range of voltages. In addition, stimuli can be subject to precise timing control.
In addition to supporting an ON mode, in which a driver""s output signal varies in proportion to its input signal, driver circuits for ATE generally also support a xe2x80x9ctristatexe2x80x9d mode. In tristate, a driver""s output impedance goes to a high value and consequently its output current goes substantially to zero. Most test procedures require that driver circuits switch between ON mode and tristate mode at high speed, and at precisely controlled instants in time. For ATE applications, therefore, driver circuits should be able to switch quickly between ON mode to tristate mode.
With the foregoing background in mind, it is an object of the invention for a driver circuit to turn off and on quickly.
To achieve the foregoing object, as well as other objectives and advantages, a driver circuit includes a driver input for receiving an input signal and a driver output for producing an output signal. The driver input is coupled to respective inputs of first and second amplifiers. The first amplifier has an output configured for substantially sourcing current only, and the second amplifier has an output configured for substantially sinking current only. The outputs of the first and second amplifiers are coupled to the driver output, for producing the driver output signal. The driver circuit further includes a disable circuit having an input for receiving a drive disable signal (DD) and at least one output coupled to the first and second amplifiers. The driver circuit is constructed and arranged to drive the first and second amplifiers, in response to the DD signal, to levels that substantially cut off output current and tristate the driver circuit.